Roll firmness measuring system and process

ABSTRACT

An online roll firmness measurement system is disclosed. In one embodiment, a contact element is placed in a fixed position. A roll of material is placed in between the contact element and a support surface. Based upon the amount of force exerted on the contact element, the firmness of the roll of material may be measured. In an alternative embodiment, the contact element applies a predetermined amount of force on the roll of material but is displaced when a roll of material is placed in between the contact element and the support surface. In this embodiment, the amount of displacement of the contact element is measured which allows for the calculation of roll firmness. In one embodiment, a roll firmness device made in accordance with the present invention may be placed in a system for winding rolls and used to maintain rolls of material being formed within preset roll firmness ranges.

RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 10/704,384 filed on Nov. 7, 2003 now U.S. Pat. No.7,127,951.

BACKGROUND OF THE INVENTION

In the manufacture of paper products, such as tissue products, a widevariety of product characteristics must be given attention in order toprovide a final product with the appropriate blend of attributessuitable for the product's intended purposes. Improving the softness oftissues is a continuing objective in tissue manufacture, especially forpremium products. Softness is a perceived property of tissues comprisingmany factors including thickness, smoothness and fuzziness.

Many tissue products and other paper webs are typically formed intolarge supply rolls after being manufactured. After the supply rolls areformed, the rolls are rewound into smaller sized rolls, which aregenerally more useful for commercial purposes. For example, inconventional systems, a core is often placed onto a mandrel that iscapable of spinning so that the spinning of the mandrel in conjunctionwith the core can effectuate winding of the paper thereon.

When tissue products, however, are formed into a rolled product duringwinding and converting, the inner layers of the rolled product may tendto lose a noticeable amount of bulk due to the compressive forces thatare exerted on the base web. Lowering bulk can reduce the perceivedquality of the product. As such, a need currently exists for a processand system that controls the winding process in order to control bulkreduction.

Another problem experienced in the formation of wound products is inproducing multiple rolls of material that all have a diameter and rollfirmness within desired limits. Ideally, the rolled products should havea substantially uniform diameter and roll firmness so that there are noconsumer noticed differences between the rolls. Further, consumersdesire rolled products, especially rolled tissue products, to have aroll firmness within a desired range such that the rolls do not feel toohard or too “mushy”.

The ability to form rolled products having a substantially uniformdiameter and roll firmness also provide various other benefits duringproduction of the product. For instance, controlling roll firmness can,in some applications, increase throughput efficiency. Further, uniformproducts can be easier to package, eliminating or reducing packagingdelays that may occur if the rolls were formed with irregularproperties.

In the past, one method of measuring roll firmness was to use a Kershawroll firmness tester as described, for instance, in U.S. Pat. No.6,077,590 to Archer, et al. which is incorporated herein by reference.The Kershaw roll firmness tester is designed to measure the rollfirmness of selected individual cut rolls offline. Unfortunately, oncemeasurements are taken, it is sometimes difficult to use the data formodifying process conditions in order to improve the quality of productsproduced, due to the delay involved in obtaining the measurement.

As such, a need currently exists for a roll firmness device that iscapable of measuring the roll firmness of a roll of material shortlyafter the roll is formed. A need also exists for a system that canautomatically make process adjustments based upon online roll firmnessmeasurements.

Definitions

A tissue product as described in this invention is meant to includepaper products made from base webs such as bath tissues, facial tissues,paper towels, industrial wipers, foodservice wipers, napkins, medicalpads, and other similar products.

The Kershaw Test is a test used for determining roll firmness. TheKershaw Test is described in detail in U.S. Pat. No. 6,077,590 toArcher, et al., which is incorporated herein by reference. FIG. 5illustrates the apparatus used for determining Kershaw roll firmness.The apparatus is available from Kershaw Instrumentation, Inc.,Swedesboro, N.J., and is known as a Model RDT-2002 Roll Density Tester.Shown is a towel or bath tissue roll 200 being measured, which issupported on a spindle 202. When the test begins a traverse table 204begins to move toward the roll. Mounted to the traverse table is asensing probe 206. The motion of the traverse table causes the sensingprobe to make contact with the towel or bath tissue roll. The instantthe sensing probe contacts the roll, the force exerted on the load cellwill exceed the low set point of 6 grams and the displacement displaywill be zeroed and begin indicating the penetration of the probe. Whenthe force exerted on the sensing probe exceeds a set point, the value isrecorded. After the value is recorded, the traverse table will stop andreturn to the starting position. The displacement display indicates thedisplacement/penetration in millimeters. The tester may record thisreading. Next the tester will rotate the tissue or towel roll 90 degreeson the spindle and repeat the test. The roll firmness value is theaverage of the two readings. The test needs to be performed in acontrolled environment of 73.4±1.8 degrees F. and 50±2% relativehumidity. The rolls to be tested need to be introduced to thisenvironment at least 4 hours before testing.

SUMMARY OF THE INVENTION

The present invention is generally directed to the production ofspirally wound products, such as tissue products, that have consumerdesired roll bulk and firmness values. The present invention is alsodirected to a system for producing rolls of material and to online rollfirmness measuring devices.

The roll firmness measuring device of the present invention, forinstance, in one embodiment applies a contact element against a roll ofmaterial that penetrates the roll a fixed distance. The amount of forceexerted against the contact element by the roll of material is thenrecorded. In another embodiment, however, the roll firmness measuringdevice applies a constant force to a roll of material and the distance acontact element penetrates the roll is recorded.

For example, in the first embodiment, the system of the presentinvention includes a contact element positioned a predetermined distancefrom a support surface. The predetermined distance is such that thecontact element contacts a roll of material when the roll of material isbeing supported by the support surface. A force measuring device is usedto measure the amount of force exerted against the contact element whena roll of material is placed in between the contact element and thesupport surface. From the diameter of the roll, the distance between thecontact element and the support surface and the amount of force exertedagainst the contact element by the roll of material, the firmness of aroll can be determined. In one embodiment, for instance, a correlationfactor can be used to determine the Kershaw roll firmness.

In one embodiment, the force measuring device can be, for instance, aload cell. A controller, such as a microprocessor, can be placed incommunication with the force sensing device for automaticallycalculating the firmness of a roll.

In calculating the firmness of a roll using the above system, thediameter of the roll of material can be assumed or can be measured. Inone embodiment, for example, the system can include a diameter measuringdevice for measuring the diameter of the roll in conjunction with takinga roll firmness measurement. For instance, the diameter measuring devicecan comprise a laser spaced from a light sensor. The laser may emit acurtain of light that is intercepted by a roll of material for measuringthe diameter of the roll based upon the amount of light sensed by thelight sensor. The diameter measuring device, when present in the system,can send information to the controller for use in calculating thefirmness of a roll.

In the above embodiment, the contact element is maintained in a fixedposition and the amount of force exerted on the contact element when aroll of material is placed on the support surface is measured. In analternative embodiment of the present invention, however, the contactelement can apply a predetermined amount of force against the roll ofmaterial and be movable away from the support surface when a force isexerted on the contact element that is greater than the predeterminedamount of force that the contact element exerts on the roll of material.The contact element can apply a predetermined amount of force againstthe roll of material by, for instance, carrying a predetermined amountof weight.

In this embodiment, a displacement measuring device measures thedisplacement of the contact element from an engagement position to afinal position when a roll of material is placed in between the contactelement and the support surface. From this information, the firmness ofthe roll can be calculated.

The displacement measuring device may be, for instance, a potentiometer.A controller, in this embodiment, can also be used to automaticallycalculate the firmness of a roll by receiving information from adiameter sensing device and the displacement measuring device. In otherembodiments, the controller can calculate the firmness of a roll withoutreceiving any information regarding the diameter of the roll. Forinstance, the diameter of the roll can be assumed to be constant or maynot be required if a plurality of contact elements are used on the sameroll of material.

Because the system of the present invention is capable of measuring thefirmness of a roll of material online or at least close in time to theproduction of the roll, various open loop or closed loop controls may beadded to the system for ensuring that the rolls of material beingproduced have uniform and desired properties.

For example, in one embodiment, the system of the present inventionincludes a caliper control device for controlling the caliper of a webof material. A log winding device receives the web of material from thecaliper control device and winds the web of material into a roll. In oneembodiment, the log winding device can comprise a winding cam and can beprogrammed to wind the web of material into a roll under determinedtension.

A roll firmness device determines a roll firmness value for selectedrolls of material wound by the log winding device. A controller, such asa microprocessor, may be in communication with the roll firmness deviceand the caliper control device. The controller can control the calipercontrol device in order to selectively increase or decrease the caliperof a web of material based upon the roll firmness value determined fromthe roll firmness device. For example, the controller can be configuredto cause the caliper control device to decrease the caliper of a movingweb if the roll firmness value of a previously formed roll is outside apreset limit indicating that the roll is firmer than desired. In alikewise manner, the controller can also be configured to cause thecaliper control device to increase the caliper of a moving web if theroll firmness value of a previously formed roll is outside a presetlimit indicating that the roll is less firm than desired.

Through the system and process of the present invention, rolls ofmaterial having desired characteristics may be repeatedly produced. Theprocess includes the steps of winding a web of material into a rollhaving a known diameter. The roll of material is then placed on asupport surface and a known load is applied to a surface of the roll ofmaterial at a known distance from the support surface. From thisinformation, a roll firmness value may be calculated. Based upon thecalculated roll firmness value, a caliper control device may then beadjusted for selectively increasing or decreasing the caliper of the webof material prior to being wound into a roll.

Other objects and features of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one of ordinary skill in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures in which:

FIG. 1 is a perspective view of one embodiment of a system for producingrolls of material in accordance with the present invention;

FIG. 2 is a perspective view of one embodiment of a roll firmness devicemade in accordance with the present invention;

FIG. 3 is a perspective view of another embodiment of a roll firmnessdevice made in accordance with the present invention;

FIG. 4 is a perspective view of still another embodiment of a rollfirmness device made in accordance with the present invention; and

FIG. 5 is a perspective view of a prior art Kershaw roll firmnessmeasurement device.

Repeated use of reference characters in the present specification anddrawings is intended to represent the same or analagous features orelements of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentinvention, which broader aspects are embodied in the exemplaryconstruction.

In general, the present invention is directed to a process and systemfor producing layered sheet products. The layered sheet products mayinclude stacked products and wound products of, for instance, facialtissues, bath tissues, paper towels, wet wipes, industrial wipers, andthe like. For instance, the present invention is particularly wellsuited to the construction of spirally-wound tissue products, such aspaper towels and bath tissues. Through the process and system of thepresent invention, layered products having substantially uniform anddesired characteristics may be produced. For example, through the systemof the present invention, spirally-wound products may be formed thathave a diameter and a roll firmness within desired parameters. Thecapability of producing roll products having uniform characteristicsprovides various advantages. For instance, by producing products withuniform properties, process throughput efficiency is increased.

More particularly, the present invention is directed to a firmnessmeasurement device that is capable of measuring the firmness, such asthe roll firmness, of a multi-layered product either online or shortlyafter the product is formed. In the past, roll firmness was generallymeasured offline on selected rolled products at a relatively slow pace.Consequently, the roll firmness measurements were not available untilmany further products had already been produced. Further, if the rollfirmness values were outside of desired limits, relating the data towinder or raw material conditions was very difficult due to the delaybetween the winding process and the point at which the roll firmnessmeasurement was taken.

By providing an online roll firmness measurement device, however, rollfirmness measurements may be provided immediately after the product isformed allowing for operators to make quick adjustments to the equipmentused to form the rolls of product in order to produce uniform productshaving desired characteristics. In fact, the online roll firmnessmeasurement device of the present invention may be electrically coupledto various pieces of equipment in a closed loop or open loop fashion formaking almost instantaneous changes and adjustments in the windingprocess.

It should be understood, however, that even though the system of thepresent invention is well suited to producing online roll firmnessmeasurements, the roll firmness device of the present invention need notbe placed online. In fact, the system of the present invention mayprovide various benefits and advantages when used offline as well.

Referring to FIG. 2, one embodiment of a roll firmness device generally10 made in accordance with the present invention is illustrated. Asshown, a roll of material 12 that may have just been formed is forwardedon a support surface to the roll firmness device 10. In this embodiment,the support surface is a moving conveyor 14. It should be understood,however, that in an alternative embodiment, the support surface may bestationary and the roll firmness device 10 may move into contact withthe roll of material. Further, instead of a conveyor, the supportsurface may comprise a mandrel on which the roll is held.

The roll firmness device 10 is shown in conjunction with a diametermeasuring device 16 that measures the diameter of the roll of material.In this embodiment, the diameter measuring device 16 includes a pair offocused light sources or lasers 18 and a corresponding pair of lightsensors 20 positioned opposite the lasers 18. The lasers 18 emit acurtain of light that is sensed by the light sensors 20. The curtain oflight can, for instance, have a width of approximately one inch such asfrom about 0.8 inches to about 1.2 inches. Further, the curtain of lightfrom each laser is emitted at a particular height with reference to theconveyor 14. When using two lasers as shown in FIG. 2, the lasers may bepositioned at different heights in a stepwise manner.

The laser beam that is emitted by the lasers 18 may be non-penetratingbeams. Non-penetrating laser beams may be provided, for example, by agas laser, a solid-state laser, a liquid laser, a chemical laser, asemiconductor laser, and the like.

As shown, when the roll of material 12 is moved on the conveyor 14adjacent to the diameter measuring device 16, the roll of materialintersects the curtains of light being emitted by the lasers 18. Lightsensors 20 measure the difference in light intensity caused by theintersection of the light curtains. This information can then be used todetermine the diameter of the roll 12. By way of example, the laser beamor beams may have a height of about 24 mm (about 1 inch). Therefore, thediameter of the roll of material is incrementally measurable based onthe light sensors 20 receiving from between about 0 to 24 millimeters ofthe 24 millimeter laser beam. More specifically, a portion of the 24millimeter laser beam is blocked by the roll of material or log whileanother portion of the beam is received by the light sensors andconverted to the diameter.

Converting the passed-through or received laser beam portion to thediameter is accomplished by the laser assembly which sends, forinstance, a 20 milliamp signal to a controller when no portion of thelaser beam is being blocked. In other words, the 20 mA signal isproduced if the entire 24 mm laser beam is received by the lightsensors. Similarly, the laser assembly is configured to send a nominalsignal, such as a 4 mA signal to a controller when the laser beam isentirely blocked by the roll of material. Thus, a 4 mA equates to nolight being received by the light sensors. In general, the laser beam isadjusted to have a particular height such that half of the beam isblocked when a roll of material at a target diameter is placed on theconveyor. When further rolls of material are placed on the conveyor, thediameter of the roll is determined from the amount of light that isblocked by the roll.

It should be noted that a 4 to 20 milliamp signal, which corresponds to0 to 24 mm, is by way of example only. For instance, a laser assemblycan be provided which uses any suitable milliamp range. Numerous othersignal ranges are contemplated to accommodate various lasers fromdifferent manufacturers and/or to accommodate specific userrequirements.

The diameter measuring device as described above is also disclosed inU.S. patent application Ser. No. 10/172,799 filed on Jun. 14, 2002 toSartain et al, which is incorporated herein by reference in itsentirety.

It should be understood, however, that any suitable diameter measuringdevice may be used in the system of the present invention. For example,in other embodiments, the diameter measuring device may reflect lightoff of the top of the roll to measure the diameter of the roll.Optionally, a wheel or roller may make contact with the roll of materialfor measuring the diameter.

It should also be understood that a diameter measuring device iscompletely optional. For example, in one embodiment, the system canassume a diameter for a roll of material. In this embodiment, forinstance, the diameter of the rolls of material as they are produced maybe measured intermittently simply to ensure that the diameter of therolls of material are within preset limits. Roll firmness measurementsas described below may occur based upon a diameter assumption.

As shown in FIG. 2, downstream of the diameter measuring device 16 is acontact element 22 that contacts the roll of material 12. As shown,contact element 22 is a wheel or a roller. In other embodiments,however, a stationery shoe may be used that has a low friction surface.The contact element 22 is maintained a particular distance from thesupport surface or conveyor 14. This distance may be adjusted manuallyusing a brake device 24. It should be understood, however, that anysuitable mechanism may be used in order to adjust the position of thecontact element.

As the roll of material 12 passes under the contact element 22, the roll12 exerts a force against the contact element 22. The amount of forceplaced against the contact element is measured by a force measuringdevice 26, such as a load cell. The load cell may be, for instance, inone embodiment a strain gauge. As also shown in FIG. 2, the contactelement also displaces into the roll of material 12 as the roll passesbelow the contact element. The distance the contact element 22 isdisplaced into the roll of material 12 depends on the diameter of theroll of material and the height of the contact element.

From the diameter of the roll of material 12, the distance between thecontact element 22 and the conveyor 14, and from the amount of forcemeasured by the load cell 26, a roll firmness value may be calculated.

In one embodiment, it may be desirable to create a callibrationcorrelation for the roll firmness device prior to use in a process. Forexample, empirical data may be accumulated and the data can be used tosolve the following equation:

${\frac{1}{Load} + \frac{1}{Displacement} + {constant}} = {{Roll}\mspace{14mu}{{Firmness}.}}$The above empirical equation can then be plotted for forming a curve.This curve may then be used to evaluate any roll firmness value that islater obtained.

If desired, the roll firmness made by the roll firmness device may becorrelated into a Kershaw roll firmness value. For example, the Kershawroll firmness may be calculated in units of distance such asmillimeters.

For many products, particularly tissue products, the rolls of materialsshould have a Kershaw roll firmness within a consumer desired range. Ingeneral, the Kershaw roll firmness of a tissue product, for instance,may be between about 6 mm to about 10 mm, and particularly between about6 mm and about 8 mm.

Through the roll firmness device 10 as shown in FIG. 2, roll firmnessvalues may be calculated shortly after the roll of material 12 isformed, allowing for quick or immediate adjustments to be made duringthe winding process for maintaining the rolls of material within desiredranges.

In the embodiment illustrated in FIG. 2, the contact element 22 may bemaintained at a particular height as rolls of material are carried alongthe conveyor 14. Alternatively, the contact element 22 may move betweenan engagement position where the contact element 22 contacts the roll ofmaterial and a disengagement position in which the contact element doesnot contact the roll of material. For example, in one embodiment, whenthe roll of material 12 is sensed by the diameter measuring device 16,an actuator may be activated causing the contact element 22 to move froma disengagement position to an engagement position for taking ameasurement. The actuator can be, for instance, a pneumatic or hydrauliccylinder, a roller screw, or a linear motor. The contact element 22 maymove along a linear pathway or may pivot into place. By moving betweenan engagement position and a disengagement position, the contact elementonly contacts the roll of material 12 when a roll firmness measurementis desired.

The roll firmness device 10 may take roll firmness measurements at asingle location on the roll of material 12 or along the entire length ofthe roll. By taking multiple roll firmness readings along the length ofthe roll of material, variations of firmness values within the rollitself may be discovered, which may indicate that the rolls of materialare not being wound properly. This data may ultimately be used toimprove product consistency and uniformity.

To prevent the contact element 22 from causing damage to the roll ofmaterial 12 or to prevent the roll firmness device from being damaged,in one embodiment, the roll firmness device 10 can include a safetyrelease device that releases the contact element from an engagementposition when a force exerted against the contact element exceeds apreset limit. When the safety release device is activated, an alarm,such as an audible or visible alarm may also be set off in order toalert an operator.

In the embodiment illustrated in FIG. 2, the contact element 22 isplaced in a fixed position and a force measuring device 26 measures theamount of force exerted against the contact element when the roll ofmaterial is passed below the contact element. Referring to FIG. 3, analternative embodiment of a roll firmness device generally 110 is shown.In this embodiment, a contact element 122 applies a fixed amount offorce to a roll of material 112. The contact element 122 is alsomovable. The amount of movement or displacement of the contact element122 is then measured in order to calculate the roll firmness.

More particularly, as shown in FIG. 3, the roll firmness device 110includes a diameter measuring device 116 similar to the embodimentillustrated in FIG. 2. A roll of material 112 is conveyed on a conveyor114 into contact with the contact element 122. The contact element 122is initially placed a predetermined distance from the conveyor 114 thatis controlled by a brake 124.

In this embodiment, the contact element 122 is associated with a firstweight 128 and a second weight 130. The weights 128 and 130 are selectedsuch that the contact element applies a predetermined amount of forceonto the roll of material 112.

As shown, the contact element 122 may pivot about a pivot point 132.When the roll of material 112 is positioned below the contact element122, the roll of material causes the contact element to pivot a distanceaway from the conveyor 114. This distance is then measured by adisplacement measuring device 134.

The displacement measuring device 134 may be any suitable instrumentcapable of measuring the displacement of the contact element 122. In oneembodiment, for instance, the displacement measuring device 134 may be apotentiometer. Alternatively, a laser may be used to directly measurehow much the contact element 122 has displaced into the roll of material112.

By knowing the diameter of the roll of material 112, the amount of forceapplied to the roll of material by the contact element 122, and byknowing the amount the contact element displaces when a roll of materialis positioned below the contact element, one can calculate a rollfirmness value for the roll of material. Similar to the embodimentillustrated in FIG. 2, this roll firmness value may be correlated to aKershaw roll firmness value.

Thus, in the embodiment illustrated in FIG. 3, a constant force isapplied to the roll of material and the displacement of the contactelement is measured. The amount of force exerted onto the roll ofmaterial 112 by the contact element may be varied as desired. Forexample, more or less weight may be applied to the contact element. Inan alternative embodiment, the contact element may be in operativeassociation with a pneumatic or hydraulic cylinder that applies thepredetermined amount of force to the roll of material.

In the embodiment shown in FIG. 3, the contact element 122 pivotsbetween an engagement position and a final resting position when theroll of material 112 is positioned below the contact element. In analternative embodiment, however, as shown in FIG. 4, the contact element122 may be positioned on a linear track 136 that allows the contactelement 122 to move up and down. In this embodiment, the contact element122 is placed in association with a weight 128.

Similar to the description of the embodiment illustrated in FIG. 2, thecontact element 122 in FIGS. 3 and 4 may also be connected to anactuator that moves the contact element from an engagement position to adisengagement position. As described above, in this manner, the roll ofmaterial 112 is only contacted by the contact element 122 when ameasurement is desired.

Since the roll firmness device of the present invention is capable ofonline roll firmness measurements, the roll firmness device is wellsuited to being integrated into a winding process. Once integrated intoa winding process, roll firmness measurements may be taken as desiredand the information obtained from the roll firmness device may be usedto control various equipment in the process in order to produce rolls ofmaterial having substantially uniform and desirable characteristics.

For example, one embodiment of a system for forming rolled products isillustrated in FIG. 1. Although the system in FIG. 1 may form rolls ofany type of material, the system is particularly well suited for formingpaper rolls, such as rolls of bath tissue or paper towels. Such productsare typically formed from pulp fibers, have a bulk of at least 2 cc/g,and may have a basis weight of from about 6 gsm to about 120 gsm, suchas from about 10 gsm to about 80 gsm.

As shown in FIG. 1, in this embodiment, a web of material 40 is firstfed through a caliper control device 42. The caliper control device 42may be, for instance, a calendering device containing a top roller 44spaced from a bottom roller 46. The rollers 44 and 46 form a nip throughwhich the web of material 40 is fed. By applying pressure to the web,the thickness or caliper of the web may be reduced.

When using a calendering device, the calendering device may be a gapcalendering device or a contact calendering device. Further, the rollers44 and 46 may be steel rollers, rubber-coated rollers, or mixturesthereof.

In addition to a calendering device, any suitable caliper control devicemay be used in accordance with present invention. For example, in analternative embodiment, an embossing device may be used in order tocontrol the caliper of the web. In still another alternative embodiment,the caliper may be controlled by adjusting tension in the web as the webis wound. For example, tension in the web can be increased or decreasedusing a dancer roll, which are well known in the art.

From the caliper control device 42, the web of material 40 is fed to alog winding device. In general, any suitable long winding device may beused in accordance with the present invention. For instance, the windingdevice may be a surface winding device, a center winding device, acoreless winding device, and the like.

In the embodiment shown in FIG. 1, the log winding device isincorporated into a turret assembly generally 48. As shown, the turretassembly 48 includes a turret 50 attached to various mandrels. Turret 50can generally be indexed into a variety of positions during the windingprocess. For instance, the indexing can occur by rotating the turret 50about its longitudinal axis. The rotation of the turret can beaccomplished by any variety of methods known in the art.

In the embodiment illustrated in FIG. 1, six mandrels 1, 2, 3, 4, 5 and6 are rotatably affixed to the turret 50. Although the turret assembly48 is depicted as including six mandrels, it should be understood thatonly one mandrel or any number of mandrels greater than one can beaffixed to the turret 50. In other embodiments, it should be understoodthat a turret assembly is not needed. For instance, in an alternativeembodiment, a surface winder may be used.

The winding process is generally initiated by placing a core 7 onto themandrel 3 according to any method known in the art. The position ofmandrel 3 as shown in FIG. 1 may be described as the “core loadingposition” of the turret 50. Once the core 7 is placed onto the mandrel3, the turret 50 can then be indexed into an “adhesive applicationposition”, which is the position occupied by mandrel 4 in the embodimentshown. In this position, any suitable adhesive (not shown) can beapplied to the core 7 by any method known in the art.

Once an adhesive is applied to the core 7, the turret 50 is once againrotated moving the core into a “prespin position”, which is the positionoccupied by mandrel 5. At the “prespin position”, the mandrel can berotated to ensure that the mandrel achieves a certain rotational speedbefore the web of material 40 is wound on the core 7. In one embodiment,as shown in FIG. 1, the mandrel 5 can be “prespun” in acounter-clockwise direction.

Once initially rotated at the “prespin position”, the mandrel can thenbe indexed by the turret 50 into a “winding position”, which is theposition occupied by mandrel 6. The rotational speed of the mandrelimparted at the “prespin position” is generally greater than the feedspeed of the web of material 40 such that, as the rotating mandrel isindexed into the “winding position”, the web of material 40 can windaround the mandrel. In particular, a leading edge of the web of material40 contacts the adhesive on the core 7 which secures the web of materialto the core as winding continues.

The rotational speed of the mandrel 6 at the “winding position” iscontrolled by any suitable log winding device, such as a winding cam 52.In one embodiment, for instance, the winding cam 52 may vary therotational speed of the mandrel 6 as the size of the roll increases inorder to maintain the web of material 40 under constant tension.

After the web of material 40 is wound onto the core 7 at the mandrel 6,the mandrel may then be indexed by the turret 50 into a “tail seal andremoval position”, which is the position occupied by mandrel 1 in theembodiment illustrated in FIG. 1. At the “tail seal and removalposition”, the end portion of the paper web 40 can be sealed to the rollof material using any suitable sealing device. The sealing device may beconfigured, for instance, to apply glue or some other adhesive to theend of the web of material such that the tail can be sealed to the roll.

Once the end of the web of material has been sealed, the finished roll12 may then be removed onto the conveyor 14 as described in FIG. 2. Asdescribed above, the conveyor 14 transports the roll of material 12 intocontact with the roll firmness device 10. The roll firmness device 10takes one or more roll firmness measurements. The roll of material 12,if desired, may then be cut into smaller lengths as shown in FIG. 1 andpackaged for consumer use.

As shown in FIG. 1, the system of the present invention further includesa controller 54, such as a microprocessor. The controller 54 is placedin communication with a caliper control device 42, the winding device52, the diameter measuring device 16, and the load cell 26. Thecontroller may be configured, for instance, to calculate a roll firmnessvalue for the roll of material 12 and, based on this information, tothen control the caliper control device 42 and/or the winding cam 52should the diameter of the roll of material 12 or the measured firmnessof the roll be outside preset limits. Specifically, the controller 54can be configured to make adjustments in the thickness of the sheet ofmaterial 40 and/or in the amount of tension that is placed upon the webof material during winding. Through the system, the diameter of therolls of material produced and/or the firmness of the rolls of materialproduced may be controlled within preset limits such that every rollproduced has substantially uniform and desirable characteristics.

For example, in one embodiment, the winding device 52 may bepreprogrammed to wind the web of material into a roll according to aparticular winding profile. Once the rolls are formed, roll firmnessmeasurements may be made using the roll firmness device 10. A rollfirmness value may be calculated by the controller 54. Based upon thecalculated roll firmness values, the controller 54 can then beconfigured to control the caliper control device for selectivelyincreasing or decreasing the caliper of the web of material 40. Forexample, the controller can be configured to cause the caliper controldevice to decrease the caliper of the moving web if the roll firmnessmeasurements are outside a preset limit indicating that the roll isfirmer than desired. Similarly, the controller can also be configured tocause the caliper control device to increase the caliper of the movingweb 40 if the roll firmness measurements are outside a preset limitindicating that the roll is less firm than desired.

The above process may also be used to maintain the diameter of the rollsof material within preset limits. Through the roll firmness device ofthe present invention, diameter and firmness adjustments may be madeinstantaneously instead of being checked periodically as is donecurrently.

In one alternative embodiment, as shown in FIG. 1, the system of thepresent invention can further include at least one caliper sensor. Forexample, the system can include a first caliper sensor 62 positionedafter the calendering device 42 and an optional second caliper sensor 60positioned before the calendering device 42. The caliper sensors 62 and60 may be used to measure the sheet caliper and to modify thecalendering load to produce a constant caliper. The caliper sensors mayalso be used to correct for changing incoming raw materials or othertransient process conditions. In general, any suitable caliper-sensingdevice known in the art may be used. The caliper sensor 62 and 60, forinstance, may determine the caliper of a web mechanically and/orelectronically.

When using two caliper sensors as shown in FIG. 1, the downstreamcaliper sensor 62 may be used to correct caliper in a feedback manner,while the upstream caliper sensor 60 may be used in a feed-forwardcontrol. The combination of the readings obtained from the calipersensors 60 and 62 may allow for the correction of short-term variationin the system. The roll firmness device 10 may then modify the caliperset point to maintain the required firmness as described above.

In one particular embodiment, the caliper sensors 62 and 60 may be usedto form a control loop for maintaining a constant caliper. The rollfirmness device 10 in conjunction with the controller 54 may then beused to change the caliper set point so that the rolls being producedfall within a target firmness value. In essence, in this embodiment, thesystem includes two control loops, namely a fast inner loop to controlcaliper and a slower outer loop to control the resulting firmness. Inthis embodiment, controller 54 may be used alone or in conjunction withfurther controllers. For example, a separate controller may be used forthe caliper control loop.

In another embodiment of the present invention, the caliper controldevice 42 may be fixed at a particular position and the controller 54may be used to make adjustments to the winding device 52 in response todiameter and roll firmness measurements received from the roll firmnessdevice 10.

In still another embodiment of the present invention, the controller 54can be configured to control the caliper control device 42 and thewinding device 52 simultaneously based upon measurements received fromthe roll firmness device 10.

Through the system of the present invention, as described above, rollsof material can be produced having uniform and desired firmness valuesand diameters. Various other advantages are also possible through thepresent invention, however. For instance, the system of the presentinvention can also be used to control the caliper of the web of material40 that is presented to the winding device. By controlling the caliperof the web, the amount of tension placed on the web during winding andthe roll firmness characteristics of the rolls, the sheet width withinthe finished rolls is also controlled. If the sheet width within therolls were irregular, for example, when cut, the material layerscontained in the rolls may have a tendency to shift. Further, irregularsheet width within the rolls can also lead to misalignments of a designthat has been printed onto the material.

For instance, in some embodiments, designs are printed upon the web ofmaterial 40. By producing rolls that have uniform firmness and diametervalues, print registration on a cut roll may be improved. In the past,print patterns had a tendency to fall out of alignment when the rolls ofmaterial were cut after being wound due to sheet width irregularities.Through the process of the present invention, this problem may beminimized.

In the embodiments shown in the drawings, a conveyor 14 is used to movethe rolls of material into contact with the roll firmness measuringdevice. In other embodiments, however, it should be understood that theroll firmness measuring device may be placed at different locations inthe system. For example, in one embodiment, the roll firmness device maybe placed adjacent to the mandrel 2. In this embodiment, roll firmnessmeasurements may be taken prior to unloading the roll of material fromthe mandrel.

In still another embodiment, the roll firmness device of the presentinvention may be used at other manufacturing locations. For example, theroll firmness device of the present invention is particularly wellsuited for use during consumer packaging of the rolled products. Theroll firmness device may be used online as the products are beingpackaged or may be set up offline in order to selectively test certainrolls prior to packaging. In this embodiment, for example, the rollfirmness device may be used to determine whether a roll has a particulardiameter and/or roll firmness suitable for packaging. If the roll doesnot fall within preset limits, the roll may be discarded or recycled.Further, should one or more rolls fall outside preset limits, acontroller may be used to automatically make adjustments to the processline, such as to the packaging equipment, in order to provide correctivefeedback.

Irregular rolls may interfere with the packaging of the products,especially when multiple rolls are being packaged in the same container.An irregular sized roll may, for instance, cause the packaging to tearor cause the packaging equipment to malfunction. By using the rollfirmness device of the present invention to remove rolls without desiredcharacteristics, packaging delays may be minimized.

The present invention may be better understood with reference to thefollowing example.

EXAMPLE

In this example, a system for measuring the firmness of a roll ofmaterial was constructed similar to the apparatus illustrated in FIG. 2.Rolls of SCOTT® paper towels produced by the Kimberly-Clark Corporationwere measured using the apparatus in order to develop a calibrationcorrelation for the roll firmness device as described above. Over 70rolls were measured using the device. The empirical data was plotted inorder to solve for the following equation:

${\frac{1}{Load} + \frac{1}{Displacement} + {constant}} = {{Roll}\mspace{14mu}{{Firmness}.}}$

The following result was obtained:

${{Roll}\mspace{14mu}{Firmness}} = {\frac{3463.97}{{Load}\mspace{14mu}{Average}} - \frac{35.636}{{Displacement}\mspace{14mu}{Average}} + 6.55078}$

From the above equation, roll firmness values may be established forrolls of material tested by the apparatus. Further, it is believed thatthe above equation will provide roll firmness data for other types ofcommercial products tested on the apparatus in addition to the SCOTT®paper towels.

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments may beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to limit the invention sofurther described in such appended claims.

1. A system for measuring the firmness of a roll of material comprising:a contact element positioned a fixed and predetermined distance from asupport surface, the predetermined distance being such that a roll ofmaterial contacts the contact element when the roll of material issupported by the support surface; and a force sensing device formeasuring the amount of force exerted against the contact element when aroll of material is placed in between the contact element and thesupport surface, wherein the firmness of a roll is determined from thedistance between the contact element and the support surface, and theamount of force exerted against the contact element by the roll ofmaterial.
 2. A system as defined in claim 1, wherein the force sensingdevice comprises a load cell.
 3. A system as defined in claim 1, whereinthe contact element comprises a roller or a wheel.
 4. A system asdefined in claim 1, wherein the support surface comprises a conveyor. 5.A system as defined in claim 1, wherein the contact element is movablebetween an engagement position and a disengagement position, theengagement position placing the contact element the predetermineddistance from the support surface.
 6. A system as defined in claim 1,wherein the support surface comprises a mandrel.
 7. A system as definedin claim 1, further comprising a diameter measuring device for measuringthe diameter of a roll of material, the measured diameter being used todetermine the firmness of a roll.
 8. A system as defined in claim 7,wherein the diameter measuring device comprises a laser spaced from alight sensor, the laser emitting a curtain of light that is intersectedby a roll of material for measuring the diameter of the roll based uponthe amount of light sensed by the light sensor.
 9. A system as definedin claim 7, further comprising a controller in communication with thediameter measuring device and the force sensing device, the controllerbeing configured to calculate a firmness value for a roll of material.10. A system as defined in claim 9, wherein the controller comprises amicroprocessor.
 11. A system as defined in claim 9, wherein thecontroller is configured to calculate a Kershaw roll firmness value. 12.A system as defined in claim 5, wherein the contact element is mountedalong a track for moving the contact element between the engagementposition and the disengagement position.
 13. A system as defined inclaim 5, wherein the contact element pivots between the engagementposition and the disengagement position.
 14. A system as defined inclaim 9, further comprising a caliper control device that is positionedto receive a web of material prior to the material being wound into aroll, the caliper control device controlling the caliper of the web ofmaterial prior to being wound into the roll, and wherein the controlleris in communication with the caliper control device, the controllerbeing configured to control the caliper control device for increasing ordecreasing the caliper of a web of material based upon a calculated rollfirmness value.
 15. A system as defined in claim 14, wherein the calipercontrol device comprises a calendering device.
 16. A system as definedin claim 1, wherein the contact element is adjustable for adjusting thedistance between the contact element and the support surface.
 17. Asystem as defined in claim 1, further comprising a safety release devicethat releases the contact element from its position when a force exertedagainst the contact element exceeds a preset limit.
 18. A system asdefined in claim 14, wherein the controller is configured to cause thecaliper control device to decrease the caliper of a moving web if a rollfirmness value calculated by the controller is outside a preset limitindicating that the roll is firmer than desired, and wherein thecontroller is also configured to cause the caliper control device toincrease the caliper of a moving web if a roll firmness value is outsidea preset limit indicating that the roll is less firm than desired.
 19. Asystem as defined in claim 7, wherein the contact element is moveablebetween an engagement position and a disengagement position, theengagement position placing the contact element the predetermineddistance from the support surface, and wherein the contact elementautomatically moves to the engagement position when a roll of materialis sensed by the diameter measuring device and automatically returns tothe disengagement position once the force sensing device takes ameasurement.
 20. The system as defined in claim 1, wherein the contactelement is located at an engagement position, the engagement positionbeing a predetermined distance from the support surface, thepredetermined distance being such that the contact element contacts theroll of material, the contact element applying a predetermined amount offorce against the roll of material, the contact element being movableaway from the support surface when a force is exerted on the contactelement that is greater than the predetermined amount of force exertedagainst the roll of material; and a displacement measuring devicemeasures a displacement of the contact element from the engagementposition to a final position when a roll of material is placed inbetween the contact element and the support surface, wherein thefirmness of a roll is determined from the measured displacement, and theamount of force exerted against a roll of material by the contactelement.
 21. A system as defined in claim 20, wherein the displacementmeasuring device comprises a potentiometer.
 22. A system as defined inclaim 20, wherein the displacement measuring device comprises a focusedlight beam and a light sensor that measures the reflectance of thefocused light beam.
 23. A system as defined in claim 20, wherein thecontact element is movable between the engagement position and adisengagement position.
 24. A system as defined in claim 20, wherein thesupport surface comprises a mandrel.
 25. A system as defined in claim20, wherein the support surface comprises a conveyor.
 26. A system asdefined in claim 20, further comprising a diameter measuring device formeasuring the diameter of a roll of material, the measured diameterbeing used to determine the firmness of a roll.
 27. A system as definedin claim 26, wherein the diameter measuring device comprises a laserspaced from a light sensor, the laser emitting a curtain of light thatis intersected by a roll of material for measuring the diameter of theroll based upon the amount of light sensed by the light sensor.
 28. Asystem as defined in claim 26, further comprising a controller incommunication with the diameter measuring device and the displacementmeasuring device, the controller being configured to calculate afirmness value for a roll of material.
 29. A system as defined in claim28, wherein the controller comprises a microprocessor.
 30. A system asdefined in claim 28, wherein the controller is configured to calculate aKershaw roll firmness value.
 31. A system as defined in claim 20,wherein the contact element is configured to pivot away from theengagement position when a force is exerted on the contact element thatis greater than the predetermined amount of force exerted on a roll ofmaterial.
 32. A system as defined in claim 20, wherein the contactelement moves along a linear track away from the engagement positionwhen a force is exerted on the contact element that is greater than thepredetermined amount of force exerted on a roll of material.
 33. Asystem as defined in claim 28, further comprising a caliper controldevice that is positioned to receive a web of material prior to thematerial being wound into a roll, the caliper control device controllingthe caliper of the web of material prior to being wound into the roll,and wherein the controller is in communication with the caliper controldevice, the controller being configured to control the caliper controldevice for increasing or decreasing the caliper of a web of materialbased upon a calculated roll firmness value.
 34. A system as defined inclaim 33, wherein the caliper control device comprises a calenderingdevice.
 35. A system as defined in claim 33, wherein the controller isconfigured to cause the caliper control device to decrease the caliperof a moving web if a roll firmness value calculated by the controller isoutside a preset limit indicating that the roll is firmer than desired,and wherein the controller is also configured to cause the calipercontrol device to increase the caliper of a moving web if a rollfirmness value is outside a preset limit indicating that the roll isless firm than desired.
 36. A system as defined in claim 33, wherein thecontact element is moveable between an engagement position and adisengagement position; and wherein the contact element automaticallymoves to the engagement position when a roll of material is sensed bythe diameter measuring device and automatically returns to thedisengagement position once the force sensing device takes ameasurement.
 37. A system as defined in claim 1, further comprising: acaliper control device; a winding cam for winding a web of material intoa roll; a roll firmness device for determining a roll firmness value fora roll of material wound by the winding cam; and a controller incommunication with the roll firmness device and the caliper controldevice, the controller controlling the caliper control device in orderto selectively increase or decrease the caliper of a web of materialbased upon a roll firmness value determined from the roll firmnessdevice.
 38. A system as defined in claim 37, wherein the roll firmnessdevice comprises: a diameter measuring device for measuring the diameterof a roll of material; the contact element; and the force sensingdevice.
 39. A system as defined in claim 38, wherein the force sensingdevice comprises a load cell.
 40. A system as defined in claim 38,wherein the contact element comprises a roller or a wheel.
 41. A systemas defined in claim 38, wherein the support surface comprises aconveyor.
 42. A system as defined in claim 38, wherein the supportsurface comprises a mandrel.
 43. A system as defined in claim 38,wherein the diameter measuring device comprises a laser spaced from alight sensor, the laser emitting a curtain of light that is intersectedby a roll of material for measuring the diameter of the roll based uponthe amount of light sensed by the light sensor.
 44. A system as definedin claim 37, wherein the controller comprises a microprocessor.
 45. Asystem as defined in claim 38, further comprising a safety releasedevice that releases the contact element from its position when theforce exerted against the contact element exceeds a preset limit.
 46. Asystem as defined in claim 37, wherein the controller is configured tocause the caliper control device to decrease the caliper of a moving webif a roll firmness value calculated by the controller is outside apreset limit indicating that the roll is firmer than desired, andwherein the controller is also configured to cause the caliper controldevice to increase the caliper of a moving web if a roll firmness valueis outside a preset limit indicating that the roll is less firm thandesired.
 47. A system as defined in claim 37, wherein the roll firmnessdevice comprises: a diameter measuring device for measuring the diameterof a roll of material; the contact element positioned at an engagementposition, the engagement position being a predetermined distance from asupport surface, the predetermined distance being such that the contactelement contacts a roll of material when the roll of material issupported by the support surface, the contact element applying apredetermined amount of force against the roll of material, the contactelement being movable away from the support surface when a force isexerted on the contact element that is greater than the predeterminedamount of force exerted on the roll of material; and a displacementmeasuring device for measuring a displacement of the contact elementfrom the engagement position to a final position when a roll of materialis placed in between the contact element and the support surface.
 48. Asystem as defined in claim 37, wherein the displacement measuring devicecomprises a potentiometer.
 49. A system as defined in claim 37, whereinthe displacement measuring device comprises a focused light beam and alight sensor that measures the reflectance of the focused light beam.